MD4-5 button freeze

We are experiencing an issue with several of our MD4-5. The issue is with any button on the MD4 whether they are parker system buttons or programed virtual digital in. Intermittently, the buttons tend to freeze therefore acting like a toggle when they are not. Please see below some points that I've noted.

1. The program is updated to its latest version of 6.05.
2. The cycle time of the MD4 during operation is 30ms.
3. The cycle utilization of the MD4 during operation is 20%.
4. The memory utilization is good.
5. The MD4 is located inside and operating at ambient temperature.

If I send a new simple program to any of these MD4, the issue will go away. I did notice, when I disable a certain amount of function groups within the program, the issue goes away. Therefore, I think its pointing to a program issue, but it seems strange to me because as mentioned above everything looks pretty good. Note: This is a multi-master system where the MD4-5 is the master. Any thoughts?